need IfAbruptCloseIterator

[ljharb]

i. Let value be ? [IteratorStepValue](https://tc39.es/ecma262/#sec-iteratorstepvalue)(iterated).

this step can throw, and if it does, iterated needs to be closed.

[bakkot]

No, we don't close iterators from errors which arise from normal consumption of that iterator. It is assumed that the iterator has had a chance to clean itself up in this case.

(I actually wrote this down here but never really linked it anywhere.)

[ljharb]

hm, you're right - i see that's the case in the other helpers; it's only when there's a per-item predicate that abrupt completions close the iterators.